Conventionally, when a vibrator used as a vibration generating system for a portable terminal device represented by a mobile phone is electrically connected to a circuit board mounted on the aforementioned portable terminal device, a method that a power supply terminal of the aforementioned vibrator and electrodes on the aforementioned circuit board are connected through a lead wire by soldering has been used. However, since it is necessary for the lead wire to be positioned and soldered on the aforementioned electrodes by a worker, the many man-hours for installation require much labor and time.
As a means to solve these problems, a vibrator having leaf spring-like power supply terminals (hereafter referred to as leaf spring terminal) is proposed. This allows a power supply to a vibrator only by pressing the power supply terminals onto the aforementioned electrodes. Since disuse of a lead wire enables not only omission of positioning work by a worker but also omission of soldering between the power supply terminals and electrodes, the proposal is effective from the viewpoint of reducing installation man-hours, labor, and time.
However, in order to form a leaf spring terminal, punching work using a die or a press is required. Therefore, manufacturing processes for vibrators, including a process for forming leaf spring terminals, are complicated and expensive. In addition, since remaining materials produced by punching with a press to manufacture the power supply terminals are scrapped, the yield of materials is not so high. Moreover, the necessity of parts for supporting the leaf spring terminals inside the vibrator results in an increase in the number of parts.
Recently assembly manufacturers that mount the vibrator on the surface of the aforementioned circuit board often request a supply of power supply terminals having various shapes. In order to satisfy these requirements using a leaf spring terminal, it is necessary to change a die from the design stage, that is to say, the shape change of the power supply terminal is complicated and takes much time. Therefore, it is difficult to manufacture a vibrator equipped with power supply terminals satisfying the requirements easily and quickly at low cost.
The leaf spring terminal easily shows a permanent set due to plastic deformation and there is a possibility that repetitive loads acting on the leaf spring terminal cause deterioration of springiness of the leaf spring terminal.
Thus a vibrator of which power supply terminals are formed using torsion coil springs that still maintain the advantages of the aforementioned leaf spring terminal and can solve the problems as shown in, for example, Patent Reference 1: Patent Application No. 2002-44904 (FIG. 1 in page 3-5), was proposed.
FIG. 21 shows a vibrator 100 equipped with the abovementioned power supply terminals. A power supply terminal 101 has a torsion coil spring portion 103 formed by winding a part of a conductive rod member 102. A portion close to an end portion 104 of the power supply terminal 101 is provided with a bending portion 105 bent at a specified angle. As shown in (A) and (B) of FIG. 22, when the vibrator 100 is mounted on a surface of a circuit board 106, the bending portion 105 is made in contact with an electrode 107 of the circuit board 106 at contact point P1.
In the abovementioned vibrator, the power supply terminal 101 is formed using a rod member 102 to make the aforementioned die unnecessary, processes and time for forming terminals are reduced, and generation of permanent set seen in the aforementioned leaf spring terminal is prevented.
However, when vibration generated by the vibrator 100 or a load acting from the outside of the aforementioned portable terminal device (for example, a drop shock load caused when a user dropped the portable terminal device) results in displacement of the relative position between the vibrator 100 and the circuit board 106, a contact point P1 of the bending portion 105 and the electrode 107 naturally shift from an original position. If an amount of shift is larger than the length or width of the electrode 107, a contact point P1 moves to the outside of the electrode 107. As a result, the power supply terminal 101 is electrically disconnected, resulting in inactivation of the vibrator 100.
Since a construction of the vibrator 100 shown in FIGS. 21 and 22 provides an electrical connection between the electrode 107 and the power supply terminal 101 at only one point, a contact point P1 easily shifts to the outside of the electrode 107 and reliability of the power supply performance to the vibrator 100 is extremely low.
In addition, a characteristic that the power supply terminal 101 shifts laterally more easily than that of a leaf spring type depending on a pressing force acting on the power supply terminal 101 when the power supply terminal is mounted on the circuit board 106 because the power supply terminal 101 is formed using a rod-shaped torsion coil spring is found. Therefore, there arises a problem that, in comparison with the leaf spring terminal, the direction of the elastic deformation of the power supply terminal 101 cannot be kept invariable and a contact position with the electrode 107 cannot be fixed, thus resulting in a problem that the efficiency of mounting the vibrator 100 on the surface of the circuit board 106 decreases.
Furthermore, a characteristic of the torsion coil spring is that a tip of the torsion coil spring easily inclines in a winding direction of the torsion coil spring (directions of arrows d and e in FIG. 21), resulting in a change of an elastic pressing force against the electrode 107. Therefore, the aforementioned elastic pressing force becomes insufficient or excessive if circumstances require. Since insufficiency of the aforementioned pressing force makes it difficult to sufficiently press the bending portion 105 of the power supply terminal 101 onto the electrode 107, generation of vibration by driving the vibrator 100 makes a contact between the electrode 107 and the power supply terminal 101 unstable, leading to fluctuation. On the other hand, since an excess of the aforementioned pressing force results in an excessively strong pressing force of the bending portion 105 acting on the electrode 107, the electrode 107 is ground by the bending portion 105 due to friction between the bending portion and the electrode caused by the vibration of the driven vibrator 100, also leading to unstable contact between the electrode 107 and the power supply terminal 101.
There also is a problem that fluctuation of a contact between the power supply terminal 101 and the electrode 107 makes an end portion 104 of the fluctuated power supply terminal in contact with and in interference with a part other than the electrode 107 mounted on the surface of the circuit board 106, leading to the incapability of providing a desired pressing load and spring performance.
Generally speaking, a vibrator to be installed to a portable terminal device is required to realize further size and weight reduction because the portable terminal device itself is required to achieve size and weight reduction, and a mounting space is reduced due to the necessity of a mounting space for other parts (such as camera lens) associated with a provision of multifunctions to the portable terminal device. Size reduction of the vibrator itself results in size reduction of the power supply terminal. Since a rod-shaped member is used for the power supply terminal made from a torsion coil spring, it is necessary to reduce a diameter of the rod-shaped member to realize size and weight reduction. Since the reduction of the diameter naturally decreases strength, the power supply terminal can be easily deformed by a sudden load acting from the outside of the portable terminal device (such as a drop shock load caused when a user dropped the portable terminal device), leading to low reliability of power supply performance of a vibrator.
The purpose of this invention presented from the viewpoint of the above problems is to provide a vibrator of which a power supply terminal is made from a torsion coil spring and which has improved reliability on an electrical connection between a power supply terminal and electrode.
In addition, the purpose of this invention is to provide a vibrator of which a power supply terminal is made from a torsion coil spring and which has improved efficiency of mounting the vibrator on the surface of the circuit board.